Method for joining materials together by a diffusion process using silver/germanium alloys and a silver/germanium alloy for use in the method

Abstract

A method for joining two elements using a silver-based alloy having a germanium content is described. The method comprises providing two elements to be joined together, at least one of the elements comprising a silver/copper/germanium alloy having a silver content of at least 77% by weight, a germanium content of between 0.4 and 7% by weight, typically from about 0.5% to about 3%, the remainder principally being copper apart from any impurities. The alloy also contains boron as a grain refiner at a concentration of greater than 0 parts per million and less than 20 parts per million, more typically less than about 10 parts per million, with working embodiments including boron in an amount of about 2 parts per million. The two elements are placed adjacent one another such that a portion of a free surface of the silver/copper/germanium alloy contacts a portion of a free surface of the other element without interposing a filler material between the two free surfaces. The two free surfaces are heated where the two elements are adjacent one another to a temperature below that of the solidus temperature of any one of the constituent materials of the elements, thereby joining the two elements by a diffusion process. A silver/germanium alloy also is described having a silver content of at least 77% by weight and a germanium content of between 0.4 and 7% by weight, which alloy contains boron as a grain refiner at a concentration of greater than 0 parts per million and less than 20 parts per million.

What is claimed is:  
     
       1. A method for joining two elements using a silver based alloy having a germanium content, comprising: 
       providing two elements to be joined together, at least one of the elements comprising a silver/copper/germanium alloy having a silver content of at least 77% by weight, a germanium content of between 0.4 and 7% by weight, the remainder principally being copper apart from any impurities, which alloy contains elemental boron as a grain refiner at a concentration of greater than 0 parts per million and less than 20 parts per million;  
       placing the two elements adjacent one another such that a portion of a free surface of the silver/copper/germanium alloy contacts a portion of a free surface of the other element without interposing a filler material between the two free surfaces; and  
       heating the two free surfaces where the two elements are adjacent one another to a temperature below that of the solidus temperature of any one of the constituent materials of the elements, thereby joining the two elements by a diffusion process.  
     
     
       2. A method according to claim  1 , where the germanium content comprises from about 0.5 to about 3% by weight. 
     
     
       3. A method according to claim  1 , where both elements to be joined comprise the silver/germanium alloy. 
     
     
       4. A method according to claim  1 , wherein the two adjacent free surfaces of the elements are heated to as low as a temperature of 500° C. 
     
     
       5. A method according to claim  1 , where the element comprising a silver based alloy having a germanium content is a powder, plating or a thin coating. 
     
     
       6. A method according to claim  1 , when used in the manufacture of items of jewelry, silverware or electrical or electronic contacts, or aerospace materials. 
     
     
       7. A method according to claim  1 , wherein a plurality of superimposed elements are joined together to create a multi-layered product. 
     
     
       8. A silver/germanium alloy having a silver content of at least 77% by weight and a germanium content of between 0.4 and 7% by weight, which alloy contains boron as a grain refiner at a concentration of greater than 0 parts per million and less than 20 parts per million. 
     
     
       9. A silver/germanium alloy having a silver content of at least 77% by weight, a germanium content of between 0.5 and 3% by weight, the remainder being copper apart from any impurities, which alloy contains boron as a grain refiner at a concentration of greater than 0 parts per million and less than about 20 parts per million. 
     
     
       10. A method for joining two elements using a silver based alloy having a copper and a germanium content, which method comprises: 
       providing two elements to be joined together, at least one of the elements consisting essentially of a silver/copper/germanium alloy having a silver content of at least 77% by weight, a germanium content of between 0.4 and 7% by weight, the remainder principally being copper apart from any impurities, which alloy contains elemental boron as a grain refiner at a concentration of greater than 0 parts per million and less than 20 parts per million;  
       placing the two elements adjacent one another such that a portion of a free surface of the silver/copper/germanium alloy contacts a portion of a free surface of the other element without interposing a filler material between the two free surfaces; and  
       heating the two free surfaces where the two elements are adjacent one another to a temperature below that of the solidus temperature of any one of the constituent materials of the elements thereby joining the two elements by a diffusion process.  
     
     
       11. A method according to claim  10 , wherein the germanium content comprises between 0.5 and 3% by weight. 
     
     
       12. A method according to claim  10 , wherein both elements to be joined comprise the silver/copper/germanium alloy. 
     
     
       13. A method according to claim  10 , wherein the two adjacent free surfaces of the elements are heated to as low as a temperature of 500° C. 
     
     
       14. A method according to claim  10 , wherein the silver/copper/germanium alloy is selected from the group consisting of: a powder; plating; and a thin coating of the silver/copper/germanium alloy. 
     
     
       15. A method according to claim  10 , when used in the manufacture of items selected from the group consisting of jewelry, silverware, electrical and electronic contacts, and aerospace materials. 
     
     
       16. A method according to claim  10 , wherein a plurality of superimposed elements are joined together to create a multi-layered product. 
     
     
       17. An alloy consisting essentially of a silver/copper/germanium alloy, the alloy having a silver content of at least 77% by weight, a germanium content of between 0.4 and 7% by weight, the remainder being copper apart from any impurities, which alloy contains elemental boron as a grain refiner at a concentration of greater than 0 parts per million and less than 20 parts per million. 
     
     
       18. An alloy according to claim  17 , wherein the germanium content comprises between 0.5 and 3% by weight. 
     
     
       19. An alloy according to claims  17 , wherein the elemental boron content is less than 10 parts per million. 
     
     
       20. An alloy according to claim  17 , wherein the elemental boron content is about 1 part per million. 
     
     
       21. An alloy according to claim  17 , wherein the boron is provided by a master copper/boron alloy having a boron content of about 2 percent by weight.